In all of the subterranean applications mentioned above, it is frequently desirable to provide a drill or boring machine which is capable of making relatively long holes or bores in a gallery wall or a rock structure forming a part of a subterranean excavation region. The bore or hole may receive an explosive charge for advancing the gallery, may be for the purpose of taking samples of the geological formations, may facilitate breaking up of material which has previously been separated from the wall, or may function itself as a means for weakening the wall or a mass of material so as to permit its further degradation.
For this purpose, various drill and borer structures have been provided heretofore.
The invention is particularly directed or concerned with machines for the purposes described which are capable of producing a plurality of parallel bores of considerable length along a gallery face to be advanced.
In recent years, it has been found to be advantageous to drill these holes substantially parallel to the gallery axis, i.e. generally horizontally since relatively long holes can be made, packed with the explosive, and used to separate more massive bodies of material in the direction of advance of the gallery. These systems are generally to be contrasted with systems in which the holes were drilled obliquely and in which the length of the hole was limited by the angle made by the axis of the drill with respect to gallery axis.
The rail or slide supports used heretofore for drilling applications have generally provided a parallelogrammatic linkage between the base and the rail, the parallelogrammatic linkage either utilizing a series of fixed mechanical links or a hydraulic system whereby fluid could be transferred from one cylinder to another. In either case, the parallelogram was of the so-called deformable type and had several significant disadvantages.
In the mechanical parallelogrammatic linkage, for instance, the direction in which the rail extended and hence the direction in which the holes were drilled, remained fixed. The apparatus had limited, if any, versatility and could not be used for anything else but simple advance of the gallery wall. However, the device was relatively simple and could produce bores which were parallel to one another with considerable accuracy.
In the case of purely hydraulic systems, there was a lack of precision in the parallelism between the holes drilled, i.e. the guide or rail could not be moved parallel to itself with sufficient accuracy. It may be pointed out that high precision in the drilling of parallel holes is a requirement when a large body of material is to be blasted loose in a subterranean system.